title: rFliC prolongs allograft survival in association with the activation of recipient Tregs in a TLR5-dependent manner.
abstract: Allorejection remains an obstacle for successful organ transplantation. Although different types of immunosuppressive agents are effective for controlling rejection and prolonging graft survival, drug treatment is limited because of side effects and toxicity. Therefore, it is necessary and urgent to identify new candidate drugs for inducing allotolerance. Recently, it has been reported that bacterial flagellin induces the immunosuppressive activity of regulatory T cells (Tregs) in humans in vitro. In the present study, we analyzed the effects of recombinant flagellin (rFliC) on allograft survival and explored the underlying mechanisms associated with the activation of recipient Tregs in a murine skin allotransplantation model. The results showed that rFliC administration (3 mg/kg, once per day for 3 days, i.p.) prolonged allograft survival (mean survival time: 18.4±1.1 days) compared to the control group (10±0.7 days, P<0.01). Additionally, higher positive expression of Toll-like receptor 5 (TLR5) was detected within the allograft administered with rFliC. The frequency of CD4(+)CD25(+)Foxp3(+) Tregs; the expression of Treg-related factors TLR5, Foxp3, TGF-β1 and IL-10; and the proliferation and suppression of Tregs were increased following rFliC administration compared to the control. Moreover, the increased expression of tolerance-related molecules and the proliferation of Tregs induced by rFliC were attenuated by an anti-TLR5 blocking antibody both in vivo and in vitro. In conclusion, rFliC administration prolongs the survival of allografts, which is associated with the activation of recipient Tregs in a TLR5-dependent manner. rFliC may be a new candidate for anti-allorejection therapy.
authors.forename: Jing
authors.initials: J
authors.lastname: Hao
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.forename: Ting
authors.initials: T
authors.lastname: Liang
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Guihua
authors.initials: G
authors.lastname: Hou
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000008:administration & dosage; D015704:CD4 Antigens / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D005408:Flagellin / Q000008:administration & dosage*; D051858:Forkhead Transcription Factors; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control*; D006085:Graft Survival / Q000187:drug effects; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000008:administration & dosage*; D016038:Skin Transplantation; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D051198:Toll-Like Receptor 5 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D019138:Antibodies, Blocking; D015704:CD4 Antigens; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D011994:Recombinant Proteins; D051198:Toll-Like Receptor 5; D005408:Flagellin